Methanol synthesis is the simple addition of hydrogen to carbon monoxide. This reaction is reversible, with the position of equilibrium determined by pressure, temperature, and concentration as follows: ##STR1##
The reaction rate of approach to equilibrium is a function of temperature alone. More particularly, as temperature increases, the reaction rate increases.
Two known commercial processes for producing methanol use uniform temperature reactors. In the first known process, hydrogen and carbon monoxide are fed to a reactor having an "optimum" temperature. An optimum temperature is sufficiently low to drive the above methanol synthesis reaction towards methanol without significantly compromising the rate of reaction. Then, the reactor is quenched in order to condense the methanol so that it can then be separated. After methanol separation, the reactor is again heated up for the next cycle.
The second known uniform-temperature methanol reactor involves passing the reactants through a boiling water reactor. Then, the exit gas from the reactor is fed to a condenser where the methanol can be separated. Subsequently, the gas is rewarmed and recycled, with the addition of fresh synthesis gas to prevent the buildup of impurities.
In each of these two known processes, the reaction is driven gradually towards completion, with only about a ten to twenty percent degree of reaction with each stage. In addition, each process requires the step of purging a certain amount of the stripped gas during each cycle, in order to prevent a significant build-up of methane and trace inerts, such as nitrogen.